1. Field of the Invention
This invention relates to an improved pyridine and alkylpyridine synthesis process. In the process for synthesizing pyridine or alkylpyridines by reacting ammonia and a carbonyl reactant in the presence of a catalyst comprising a crystalline silicate having a silca to alumina ratio of at least about 12 and a Constraint Index within the approximate range of 1 to 12, the present improvement comprises effecting higher activity, better selectively and better catalyst aging rate by using catalyst comprising said cystalline silicate having an Alpha Value of less than about 50 and a binder of amorphous silica.
2. Description of Prior Art
A method for synthesizing pyridine and alkylpyridines by reacting a carbonyl compound and ammonia over catalyst comprising a crystalline aluminosilicate zeolite having a silica/alumina mole ratio of at least 12/1 and a Constraint Index of from 1 to 12, which may or may not be composited with essentially any known binder material, including natural or synthetic materials, e.g. clays, alumina, silica-alumina and silica, and which may or may not contain a metal promoter, e.g. cadmium and copper, is taught in U.S. Pat. No. 4,220,783. U.S. Pat. No. 3,728,408 suggests the use of a catalyst comprising zeolite having a silica/alumina mole ratio greater than 10/1, preferably up to 200/1, more preferably with a maximum of 75/1, for conversion of organic polar compounds. Zeolites taught include Y, Beta, ZSM-5 with a silica/alumina ratio of up to 100, and mordenite. A reaction sugested by the latter patent is synthesis of methylpyridine from acetaldehyde and ammonia.
It is the improvement over the above cited references, each incorporated entirely herein by reference, which is the subject of the present invention.
The reaction of acetaldehyde or certain other low molecular weight aldehydes and ammonia either in the absence or presence of methanol and/or formaldehyde to yield pyridine and alkyl derivatives thereof has heretofore been carried out in the presence of amorphous silica-alumina composites containing various promoters. See, for example, U.S. Pat. No. 2,807,618. The yields of desired products using the latter catalysts have been poor.
Alkylpyridines have also been synthesized, as reported in Advances in Catalysis, Volume 18, page 344 (1968) Academic Press, Inc., New York, N.Y., by passing gaseous acetaldehyde and ammonia over the crystalline aluminosilicates NaX and H-mordenite. While initial conversion utilizing these materials as catalysts was high, catalyst deactivation by coking was rapid, providing a commercially unattractive system, characterized by poor catalyst stability.
U.S. Pat. Nos. 4,149,002; 4,147,874 and 3,946,020 teach synthesis of pyridine and/or alkylpyridines with different catalysts. The methods of U.S. Pat. Nos. 4,149,002 and 4,147,874 utilize a catalyst of highly dispersed aluminum silicate containing 3 to 30 weight percent aluminum oxide. The method of U.S. Pat. No. 3,946,020 uses a catalyst prepared by immersing silica-alumina or a silica-alumina mixture containing a promoter in an aqueous solution of ammonium halide.
A method for making an extruded silica-rich solid which may be useful as a catalyst for the present improved process is taught in U.S. Pat. No. 4,582,815 issued to E. Bowes.